1. Technical Field
The disclosed subject matter relates to a vehicular lamp, and more particularly to a light source unit contained in a vehicular lamp for the purpose of illumination in certain lighting devices, such as headlights, spot lights, traffic lights, signal lights, fog lights, etc.
2. Description of the Related Art
FIGS. 10 and 11 show examples of conventional vehicular lamps. First, a vehicular lamp 90 shown in FIG. 10 comprises a reflecting mirror 91 that is a spheroid type and configured as an upper half. An LED light-emitting element 92 or light-emitting source is attached at a first focus f1 of the reflecting mirror 91 such that the central axis of light emission is directed upward. A projection lens 93 is provided which has a focus in the vicinity of a second focus f2 of the reflecting mirror 91.
In this case, a base 94 is used to mount the LED light-emitting element 92 at an appropriate position relative to the reflecting mirror 91. The base 94 extends in the direction of the projection lens 93 and is located in the vicinity of the second focus f2. Therefore, the light emitted from the LED light-emitting element 92 forms the second focus in the vicinity of the tip 94a of the base 94, that is, in the vicinity of the focus of the projection lens 93.
The sectional shape of the light focused on the second focus may be formed in a semicircle in the first quarter by the tip 94a of the base 94. In this case, the projection lens 93 expands and inverts the above-described shape and projects the inverted shape in the direction of illumination. Thus, the inverted shape is turned into a semicircle in the last quarter, which contains little or no upward light and can provide a distribution characteristic that does not dazzle oncoming vehicles.
A vehicular lamp 100 shown in FIG. 11 comprises a plurality of semiconductor light-emitting elements 102(a-e) arranged substantially in line such that one side such as a lower side is aligned with a previously set straight line X. It also comprises a lens 104 having an optical center on the previously set straight line X. The lens receives the light emitted from the semiconductor light-emitting elements 102(a-e) and projects the combined light in the direction of illumination.
The vehicular lamp 100 is basically required to form a light distribution pattern having an extent in the horizontal direction. Accordingly, the semiconductor light-emitting elements 102(a-e) are aligned on the basis of the horizontal straight line X. A shield material 112 may be interposed between the semiconductor light-emitting elements 102(a-e) and the lens 104 to shield the upward light that dazzles oncoming vehicles.    [Patent Document 1] JP 2003-317513A    [Patent Document 2] JP 2004-247151A
In the configuration including the reflecting mirror 91 of the spheroid type provided to cover the LED light-emitting element 92 attached to project light upward (Patent Document 1), the light from the LED light-emitting element 92 located on the first focus is again focused on the second focus f2. The sectional shape of the light focused on the second focus f2 is projected to the front through the projection lens 93. Accordingly, the depth of the vehicular lamp is relatively deep and restrictions exist on the position at which the lamp can be attached which results in problems in terms of design flexibility, weight of the vehicle, etc.
In the system including the semiconductor light-emitting elements 102 arranged in line to form a light source which is analogous to the distribution characteristic, and which is projected through the lens 104, the depth can be relatively smaller. In this case, however, the light emitted from the semiconductor light-emitting elements 102 is diffused. Accordingly, the light that can be led into the lens 104 is only a partial portion of the total light. A number of high-power semiconductor light-emitting elements 102 may therefore be required to ensure a desired brightness. Thus, the full utilization of the light beams is low, which results in efficiency and other problems.